This invention relates generally to an improved method and apparatus for identifying television broadcast programs as they are received by a television receiver in the household. This invention is particularly useful in the field of test marketing but is not limited thereto. Test marketing allows businesses to test and experiment with a marketing strategy in a limited geographic area before committing to a full launch of the proposed marketing plan. Test markets are usually conducted by monitoring the behavior of a panel of households in a limited geographical area. Very precise demographic information is maintained on the households in the panel. The research generally consists of monitoring the behavior of a panel of households both before and after one or more variables in the environment have been changed. The research also consists of correlating the panelists' behavior with exposure to television commercials and other forms of advertisement. An example of one type of relationship that is of particular interest to the researcher is the relationship between the purchasing behavior of panelists and viewing of television commercials by panelists. Two types of data are required to study this relationship. First is the data related to the panelists' behavior, such as their purchasing patterns of products or services. The second type of data that is monitored is the number of exposures to a particular commercial or advertisement that the panelists receive. Sometimes the researcher monitors two or more panels of households at the same time. This technique permits inter group comparisons to be made as each group is exposed to either different types of commercials or advertisements and/or different amounts of exposure to these stimuli. The groups may be referred to as the control group and the test group.